1. Field of the Invention
This invention relates to the field of mechanical amplifier mechanisms and more specifically to the area of stroke amplifiers which use saggital linkages.
2. Description of the Prior Art
Several piezoelectric or electroexpansive actuators have been described in the prior art which are connected with levers and saggital linkages to produce motion amplification. In those cases, a high force, short stroke expansion or contraction of a piezoelectric actuator is amplified as a lower force, longer stroke movement.
In U.S. Pat. No. 4,318,023 (incorporated herein by reference), a saggitally amplified mechanism is described in which a lever arm is pivotally connected to a fixed base support and is driven for movement by an electroexpansive actuator. The end of the lever arm, opposite the pivot end, is connected to one end of a saggital tension member. The opposite end of the saggital tension member is connected to the fixed base support. Upon actuation of the electroexpansive actuator, the lever arm is pivoted to increase the tension on the saggital member and cause the midpoint of the saggital member to be moved in a direction perpendicular to the longitudinal axis defined between the end points of the saggital tension member. Such saggital amplification devices are preferred due to the inherent high rigidity, low play and lower overall mass of components that are necessary to provide amplified movement at an appropriate force for such applications as valves for liquid or air flow control or pin actuators for printer heads.
The 1980 SAE paper No. 800502 entitled "Piezomotors - Electromechanical Muscle" by O'Neill et al (incorporated herein by reference) describes in some detail the properties and construction of piezoelectric actuators that can either be shortened or lengthened when subjected to an electric field and employed in amplification devices.
U.S. Pat. No. 4,769,569 shows a piezoelectric stack motor stroke amplifier in which a rigid frame supports a pair of stack motors. The stack motors act in opposition against a movable output actuator to provide an amplified push stroke output actuation.